The present invention relates to electrical power conversion and more particularly to a system and method for converting power from one form to another.
Electrical power is typically supplied in one of two forms: direct current (DC) power and alternating current (AC) power. There are often times when it is desirable to convert from one form of power to the other form. This is accomplished by using a power converter. A power converter can convert power from AC to DC, DC to AC, AC to AC, or DC to DC. In this way, a power converter allows a device that uses one form or level of power to connect to a power source that supplies a different form or level of power.
Known power converters currently exhibit multiple problems. First, large low-frequency transformers make power converters heavy, large, and expensive. Second, power converters using high-frequency transformers are less efficient, resulting in an output power that is significantly less than the input power. Third, some power converters using high-frequency transformers can generate large voltage spikes in the output section. Fourth, in an attempt to reduce or eliminate these voltage spikes, some power converters include extra circuitry which increases their size, weight, cost, and complexity. See, for example, U.S. Pat. No. 6,067,243 versus U.S. Pat. No. 6,236,192. Fifth, a zero volt pause is another problem found with power converters using high-frequency transformers. A zero volt pause occurs when the voltage on the output pauses briefly at zero volts, such as between pulses of a pulse width modulated (PWM) output. During this brief pause, the voltage can fluctuate between a small positive and negative voltage due to noise. These voltage fluctuations can cause major problems in sensitive electronics such as furnace controllers, laser printers, and copiers.
Therefore, there is a need in the art for an efficient power converter with reduced size, weight, cost, and complexity, which does not experience large voltage spikes and exhibits a clean zero crossing.